Stop what you're doing and use that YouTube contraption of yours to cue up the sounds of Mazda's early '90s 787B Group C race car ripping around a place like Le Mans. Now try and forget what you heard. It turns out that you can't, and neither could David Mazzei, who had to go on and put together an RX-7 of specific proportions, all because of a sound.
Recall the glorious cacophony that was '90s-era Formula One and its high-revving, naturally aspirated machines and you'll start stirring up the same sort of nostalgia Mazzei did. "You won't hear them anymore," he says about the V-8s, V-10s, and V-12s that have long been retired. "The closest thing to [that sound] is the 787B's four-rotor." It's not like Mazda was selling any of the few 787Bs that exist or that Mazzei thought that was a possibility, but the likelihood of re-creating the sound that its powerplant made was something entirely doable.
Developed during that same storied Formula One period, Mazda's 787B spawned the R26B engine. At 2.6L of displacement and good for as much as 900 hp, it became the first rotary engine to power a car toward a 24 Hours of Le Mans victory. It was raw, it was ahead of its time, and it was the basis for everything Mazzei would go on and do with his third-generation RX-7. A PPRE four-rotor short-block leads the way with Mazzei's RX-7, but there's a whole lot more to the story than a guy from Alabama ordering up a ready-made block from some rotary experts in New Zealand, and then getting it to sound and perform exactly the way he'd wanted.
About that sound. "One of the biggest issues we had was the original exhaust manifold," Mazzei says. "It worked, [but] it just didn't sound right." And by "didn't sound right," he's talking about the difference between the sort of noises that his BorgWarner-turbocharged quad-rotor made versus the 787B's naturally aspirated version. He was told it couldn't be done. On the dyno it sounded like the RX-7's original 13B, and an oiling problem along with boost-control issues meant things just weren't looking good.
Frustration led to Mazzei reaching out to the experts. Experts like Carlos G. Lopez, who'd worked on Mazda's 787B in its heyday and who was smart enough to suggest changes that ought to be made to the manifold's runners and how its wastegates should be integrated. "Graciously, he shared with me details that [would allow my manifold to] match the harmonic resonance of the 787B," Mazzei says. He even told Mazzei why that external oil pump of his had failed and what he had to do to fix it. Ask Mazzei and he'll tell you that, were it not for Lopez, that four-rotor would either be in pieces or, at best, sound like the 13B the RX-7 came with in the first place.
There's a whole lot more to this RX-7 than what it sounds like, though. "In my head, I've always imagined every piece of this car," Mazzei says about the sort of things that were planned even before the car was found in its Tennessee home, broken windows, missing interior, water damage, and all. It was, as Mazzei puts it, "an abomination." For him, though, only an abomination of an RX-7 would make sense for what he had planned. Which is exactly why he sold the first one he'd bought to make way for this project. "That's what made this car the perfect candidate," he says about the wreck of a Mazda he just paid for. "Why take something that's nice and destroy it to bits to build a race car?"
And turn this RX-7—an R1 trim, mind you—into a full-blown race car is precisely what he did. Inside, the custom rollcage and carbon-fiber inserts across the dash tip you off to that just as much as the fuel surge tank and intercooler reservoir behind the driver seat do. It's all business in here and is where you'll find evidence of things like the Haltech ECU that's responsible for the conservative 800 whp this four-rotor makes on 93-octane. "I've always imagined rotary engines being [their] most reliable and enjoyable on pump gas," Mazzei says. "[But] power can't be had easily with low stress on a rotary engine unless displacement is [increased]." If you were wondering why Mazzei invested in a four-rotor short-block that costs more than the last three cars you've owned combined, that was your answer.
Tell your friends you're about to buy an RX-7 and prepare yourself for a rotary intervention led by those who've never owned one, let alone blown one up or had one of those infamous engine bay fires. "I was warned countless times by friends and family," Mazzei says, "that [an RX-7] could become a huge financial risk with multiple potential problems stemming from [its] age [to its] finicky rotary engine." That, he says, is exactly what led him to getting an RX-7 in the first place, though. "When you tell a kid 'no,' of course they'll want to find out the hard way. I had to know." It's a good thing, too, because RX-7 builds like these don't come around often, and ones that make the sort of music that Mazzei's does are simply unprecedented.
In the land of pistons and rods, more displacement is as simple as hogging out some bores and swapping a crank, but you'll always be bound by the constraints of that short-block. For the rotary, it's a whole different story. Instead of any of those pistons and rods bobbing up and down, rotary engines are made up of two or three rotors that spin around inside of their own chambers. There are no cams, no rocker arms, no valves. Here, displacement comes by way of adding more rotors. It sounds a whole lot easier than it is, though. You think you've got it made when you discover how modular Mazda's rotaries are and that, oftentimes, rotor housings can be stacked alongside rotor housings for what you think will amount to an infinite amount of displacement. And it would be that easy were it not for that eccentric shaft that slides through the center of it all and that Mazda only offered in lengths that'll accommodate the sort of two- and three-rotor engines you're familiar with, like its 13B and 20B, for instance. Get yourself the right custom eccentric shaft, though, like Mazzei's PPRE-made four-rotor's got, and you're one step closer to getting a couple of extra rotors and their housings to play nicely with that 13B of yours. Do it right and you've just gained a whole lot of torque and made that rotary about as efficient as it'll ever be.